Abrasive article having reaction activated chromophore

ABSTRACT

An abrasive article has a layer including an epoxy constituent, a cationic photointiator within the epoxy constituent, and a latent colorant configured to change color in response to activation of the cationic photoinitiator.

CORRESPONDING APPLICATIONS

The present application claims priority from U.S. Provisional PatentApplication No. 60/669,413, filed Apr. 8, 2005, entitled “ABRASIVEARTICLE HAVING REACTION ACTIVATED CHROMOPHORE,” naming the applicantXiaorong You, which application is incorporated by reference herein inits entirety.

FIELD OF THE DISCLOSURE

This disclosure, in general, relates to abrasive articles and methodsfor forming same.

BACKGROUND

Abrasive articles, such as coated abrasives and bonded abrasives, areused in various industries to machine workpieces, such as by lapping,grinding, or polishing. Machining utilizing abrasive articles spans awide industrial scope from optics industries, automotive paint repairindustries, to metal fabrication industries. In each of these examples,manufacturing facilities use abrasives to remove bulk material or affectsurface characteristics of products.

Surface characteristics include shine, texture, and uniformity. Forexample manufacturers of metal components use abrasive articles to fineand polish surfaces, and oftentimes desire a uniformly smooth surface.Similarly, optics manufacturers desire abrasive articles that producedefect free surfaces to prevent light diffraction and scattering.

Manufactures also desire abrasive articles that have a high stockremoval rate for certain applications. However, there is often atrade-off between removal rate and surface quality. Finer grain abrasivearticles typically produce smoother surfaces, yet have lower stockremoval rates. Lower stock removal rates lead to slower production andincreased cost.

Particularly in the context of fine grained abrasive articles,commercially available abrasives have a tendency to leave random surfacedefects, such as scratches that are deeper than the average stockremoval scratches. Such scratches may be caused by grains that detachfrom the abrasive article, causing rolling indentations. When present,these scratches scatter light, reducing optical clarity in lenses orproducing haze or a foggy finish in decorative metal works. Suchscratches also provide nucleation points or attachment points thatreduce the release characteristics of a surface. For example, scratchesin sanitary equipment allow bacteria to attach to surfaces, andscratches in polished reactors allow formation of bubbles and act assurface features for initiating unwanted reactions.

Loss of grains also degrades the performance of abrasive articles,leading to frequent replacement. Frequent abrasive article replacementis costly to manufacturers. As such, improved abrasive articles andmethods for manufacturing abrasive articles would be desirable.

SUMMARY

In a particular embodiment, an abrasive article has a layer including anepoxy constituent, a cationic photointiator within the epoxyconstituent, and a latent colorant configured to change color inresponse to activation of the cationic photoinitiator.

In another exemplary embodiment, an abrasive article includes a polymermatrix, a reaction activated chromophore within the polymer matrix, andparticulate abrasive grains.

In a further exemplary embodiment, an abrasive article includes areaction activated chromophore.

In an additional exemplary embodiment, a method of manufacturing anabrasive article includes initiating a curing process in an abrasivearticle workpiece. The abrasive article workpiece includes a polymerprecursor and a latent colorant. The latent colorant is configured tochange color in response to curing. The method also includes determininga target color of the abrasive article workpiece and terminating thecuring process when the abrasive article workpiece exhibits the targetcolor.

In another exemplary embodiment, a method of controlling abrasiveproduct quality includes forming an abrasive product comprising apolymeric matrix and a reaction activated chromophore. The reactionactivated chromophore is configured to exhibit a color characteristicbased on a state of curing. The method also includes inspecting theabrasive product based on the color characteristic and categorizing theabrasive product based on the color characteristic.

In a further exemplary embodiment, an abrasive article includes a layerpatterned to form a surface structure. The layer includes a materialincluding a polymeric matrix and a reaction activated chromophore, andincludes abrasive grains bonded to the layer.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure may be better understood, and its numerousfeatures and advantages made apparent to those skilled in the art byreferencing the accompanying drawings.

FIG. 1 includes an illustration of an exemplary coated abrasive article.

FIG. 2 includes an illustration of an exemplary structured abrasivearticle

FIG. 3 includes an illustration of an exemplary bonded abrasive article.

The use of the same reference symbols in different drawings indicatessimilar or identical items.

DESCRIPTION OF THE DRAWING(S)

In a particular embodiment, the disclosure is directed to an abrasivearticle having a layer that is formed of a polymer matrix. The polymermatrix includes a reaction activated chromophore configured to indicatea state of curing. In one exemplary embodiment, the reactive chromophoreincludes a latent colorant and a curing byproduct. For example, thecuring byproduct may be a byproduct of activating a photoinitiator. Theabrasive article may also include particulate abrasive grains.

In another embodiment, the disclosure is directed to a method ofmanufacturing an abrasive article. The method includes initiating acuring process on a workpiece, determining a target color exhibited bythe workpiece and terminating the curing process based on the targetcolor. The curing process may include photo curing or thermal curing.

In a further exemplary embodiment, the disclosure is directed to amethod of controlling abrasive product quality. The method includesforming an abrasive product having a polymer matrix and a reactionactivated chromophore, inspecting the abrasive product for a colorcharacteristic, and categorizing the abrasive product based on the colorcharacteristic. The color characteristic may, for example, be a targetcolor or color uniformity.

Generally, the abrasive article is formed by curing a binderformulation. The binder formulation typically includes polymerprecursors or polymerizable constituents. For example, the binderformulation may include cationically polymerizable constituents or mayinclude radically polymerizable constituents. In addition, the binderformulation includes a catalysts or an initiator, such as aphotoinitiator or a thermal intiator, to initiate and facilitate curing.In one particular embodiment, the binder formulation includes a latentcolorant. The latent colorant may react with byproduct of the curing,such as species derived from activated initiators, to change color.

The abrasive article also includes abrasive particles. In oneembodiment, the binder formulation is used as a compliant layer, a makecoat or a size coat in a coated abrasive article. Abrasive grains may bedeposited on the make coat and be overcoated with a size coat. Inanother embodiment, the abrasive grains are mixed with the binderformulation, a mold is filled with the mixture, and the mixture is curedto form a bonded abrasive article.

In an exemplary embodiment, the binder formulation includes acationically polymerizable constituent. For example, the cationicallypolymerizable constituent may have epoxy functional groups or oxeranefunctional groups.

The constituents including epoxy functional groups, also referred to asepoxy constituents, are cationically curable, by which is meant thatpolymerization or crosslinking of the epoxy group may be initiated bycations. The epoxy constituents can be monomers, oligomers or polymersand are sometimes referred to as “resins.” Such materials may have analiphatic, aromatic, cycloaliphatic, arylaliphatic, or heterocyclicstructure. The epoxy constituents may include epoxy groups as sidegroups, or the epoxy groups may form part of an alicyclic orheterocyclic ring system. Epoxy groups may also be bound to, forexample, siloxane containing backbones.

The epoxy constituent may, for example, include at least one liquidcomponent, such that the combination of materials is a liquid. Thus, theepoxy constituent can be a single liquid epoxy material, a combinationof liquid epoxy materials, or a combination of liquid epoxy material(s)and solid epoxy material(s) soluble in the liquid.

An example of a suitable epoxy constituent includes polyglycidyl orpoly(methylglycidyl) ester of polycarboxylic acid, poly(oxiranyl) etherof polyether, epoxidised unsaturated fatty acid, or any combinationthereof. The polycarboxylic acid can be aliphatic, such as, for example,glutaric acid, adipic acid and the like; cycloaliphatic, such as, forexample, tetrahydrophthalic acid; or aromatic, such as, for example,phthalic acid, isophthalic acid, trimellitic acid, or pyromellitic acid;or any combination thereof. The polyether can be poly(tetramethyleneoxide). A carboxyterminated adduct, for example, of trimellitic acid orpolyol, such as, for example, glycerol or2,2-bis(4-hydroxycyclohexyl)propane may be used. A suitable epoxidisedunsaturated fatty acid may be obtained from, for example, linseed oil orperilla oil.

A suitable epoxy constituent may include polyglycidyl orpoly(-methylglycidyl) ether obtainable by the reaction of a compoundhaving at least one free alcoholic hydroxy group or phenolic hydroxygroup and a suitably substituted epichlorohydrin. The alcohol can beacyclic alcohol, such as, for example, ethylene glycol, diethyleneglycol, or higher poly(oxyethylene) glycol; cycloaliphatic, such as, forexample, 1,3- or 1,4-dihydroxycyclohexane,bis(4-hydroxycyclohexyl)methane, 2,2-bis(4-hydroxycyclohexyl)propane, or1,1-bis(hydroxymethyl)cyclohex-3-ene; or contain aromatic nuclei, suchas N,N-bis(2-hydroxyethyl)aniline orp,p′-bis(2-hydroxyethylamino)diphenylmethane.

Alternatively, the epoxy constituent may be derived from mono nuclearphenol, such as, for example, from resorcinol or hydroquinone, or may bebased on polynuclear phenol, such as, for example,bis(4-hydroxyphenyl)methane (bisphenol F),2,2-bis(4-hydroxyphenyl)propane (bisphenol A), or on condensationproducts, obtained under acidic conditions, of phenol or cresol withformaldehyde, such as phenol novolac or cresol novolac.

A suitable epoxy constituent alternatively may include poly(N-glycidyl)compound, which is, for example, obtainable by dehydrochlorination ofthe reaction product of epichlorohydrin with an amine that comprise atleast two amine hydrogen atoms, such as, for example, n-butylamine,aniline, toluidine, m-xylylene diamine, bis(4-aminophenyl)methane orbis(4-methylaminophenyl)-methane. An exemplary poly(N-glycidyl) compoundalso includes an N,N′-diglycidyl derivative of cycloalkyleneurea, suchas ethyleneurea or 1,3-propyleneurea, or a N,N′-diglycidyl derivative ofhydantoin, such as of 5,5-dimethylhydantoin.

A further example of a suitable epoxy constituent includespoly(S-glycidyl) compound, which is a di-S-glycidyl derivative, which isderived from dithiol, such as, for example, ethane-1,2-dithiol orbis(4-mercaptomethylphenyl) ether.

An additional example of an epoxy constituent isbis(2,3-epoxycyclopentyl)ether, 2,3-epoxy cyclopentyl glycidyl ether,1,2-bis(2,3-epoxycyclopentyloxy)ethane, bis(4-hydroxycyclohexyl)methanediglycidyl ether, 2,2-bis(4-hydroxycyclohexyl)propane diglycidyl ether,3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexane,3,4-epoxy-6-methylcyclohexylmethyl-3,4-epoxy-6-methylcyclohexanecarboxylate,di(3,4-epoxycyclohexylmethyl)hexanedioate,di(3,4-epoxy-6-methylcyclohexylmethyl)hexanedioate,ethylenebis(3,4-epoxycyclohexanecarboxylate),ethanedioldi(3,4-epoxycyclohexylmethyl)ether, vinylcyclohexene dioxide,dicyclopentadiene diepoxide,.alpha.-(oxiranylmethyl)-.omega.-(oxiranylmethoxy)poly(oxy-1,4-butanediyl), diglycidyl ether of neopentyl glycol, or2-(3,4-epoxycyclohexyl-5,5-spiro-3,4-epoxy)cyclohexane-1,3-dioxane, orany combination thereof.

An epoxy resin in which the 1,2-epoxy groups are bonded to differentheteroatoms or functional groups may also be useful. Such a compoundincludes, for example, the N,N,O-triglycidyl derivative of4-aminophenol, the glycidyl ether glycidyl ester of salicylic acid,N-glycidyl-N′-(2-glycidyloxypropyl)-5,5-dimethylhydantoin,2-glycidyloxy-1,3-bis(5,5-dimethyl-1-glycidylhydantoin-3-yl)propane, orany combination thereof.

In addition, a prereacted adduct of such epoxy resin with a hardener issuitable for epoxy resin. A mixture of epoxy constituents may also beused in the binder formulation.

In a particular embodiment, an epoxy constituent includes cycloaliphaticdiepoxide. An exemplary cycloaliphatic diepoxide isbis(4-hydroxycyclohexyl)methane diglycidyl ether,2,2-bis(4-hydroxycyclohexyl)propane diglycidyl ether,3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate,3,4-epoxy-6-methylcyclohexylmethyl-3,4-epoxy-6-methylcyclohexanecarboxylate,di(3,4-epoxycyclohexylmethyl)hexanedioate,di(3,4-epoxy-6-methylcyclohexylmethyl)hexanedioate,ethylenebis(3,4-epoxycyclohexanecarboxylate),ethanedioldi(3,4-epoxycyclohexylmethyl) ether,2-(3,4-epoxycyclohexyl-5,5-spiro-3,4-epoxy)cyclohexane-1,3-dioxane, orany combination thereof.

The epoxy constituent can have a molecular weight that varies over awide range. In general, the epoxy equivalent weight, i.e., the numberaverage molecular weight divided by the number of reactive epoxy groups,is preferably in the range of 60 to 1000.

Typically, the binder formulation includes from about 10% to about 90%by weight of the epoxide constituent. Weight percentages of constituentsof the binder formulation are stated relative to the total weight of thecurable components of the composition, unless specified otherwise.

The binder formulation may include another cationically curablecomponent, such as a cyclic ether component, a vinyl ether component, acyclic lactone component, a cyclic acetal component, a cyclic thioethercomponent, a spiro orthoester component, an oxetane-functionalcomponent, or any combination thereof. In a particular embodiment, anoxetane is a component comprising one or more oxetane groups, i.e. oneor more four-member ring structures according to formula (5):

The binder formulation may also include a cationic photoinitiator.Generally, a cationic photoinitiator that, upon exposure to actinicradiation, forms cations that initiate reactions of the epoxyconstituents can be used. Such a photoinitiator includes, for example,an onium salt with anions of weak nucleophilicity. An example includeshalonium salt, iodosyl salt or sulfonium salt, such as are described inpublished European patent application EP 153904 and WO 98/28663,sulfoxonium salt, such as described, for example, in published Europeanpatent applications EP 35969, 44274, 54509, and 164314, diazonium salt,such as described, for example, in U.S. Pat. Nos. 3,708,296 and5,002,856, or any combination thereof. Another cationic photoinitiatorincludes metallocene salt, such as described, for example, in publishedEuropean applications EP 94914 and 94915. An additional suitable oniumsalt initiator or metallocene salt can be found in “UV Curing, Scienceand Technology”, (Editor S. P. Pappas, Technology Marketing Corp., 642Westover Road, Stamford, Conn., U.S.A.) Or “Chemistry & Technology of UV& EB Formulation for Coatings, Inks & Paints”, Vol. 3 (edited by P. K.T. Oldring). In a particular example, a cationic photoinitiator includesa compound of formula I, II or III below,

wherein:

R1, R2, R3, R4, R5, R6, and R7 are, independent of each other, a C6-C18aryl-group that may be unsubstituted or substituted by suitableradicals; L is boron, phosphorus, arsenic, or antimony; Q is a halogenatom or some of the radicals Q in an anion LQ_(m) ⁻ may also be ahydroxy group; and m is an integer that corresponds to the valence of Lplus 1. An example of a C6-C18 aryl group includes a phenyl, a naphthyl,an anthryl, or a phenanthryl group. A suitable radical includes alkyl,for example, C1-C6 alkyl, such as methyl, ethyl, n-propyl, isopropyl,n-butyl, sec-butyl, iso-butyl, tert-butyl, or various pentyl or hexylisomers; alkoxy, for example, C1-C6 alkoxy, such as methoxy, ethoxy,propoxy, butoxy, pentyloxy, or hexyloxy; alkylthio, such as C1-C6alkylthio, such as methylthio, ethylthio, propylthio, butylthio,pentylthio, or hexylthio; halogen, such as fluorine, chlorine, bromine,or iodine; amino; cyano; nitro; arylthio, such as phenylthio; or anycombination thereof. An example of a halogen atom Q includes chlorine orfluorine. An anion LQ_(m) ⁻ may include BF₄ ⁻, PF₆ ⁻, AsF₆ ⁻, SbF₆ ⁻,SbF₅(OH)⁻, or any combination thereof. In a particular example, thephotoinitiator includes a compound of formula III wherein R5, R6, and R7are aryl, such as phenyl, biphenyl, or any combination thereof.

In another example, the photoinitiator includes a compound of formula(IV)[R₈(Fe^(II)R₉)_(c)]_(d) ^(+c)[X]_(c) ^(−d),  (IV)

wherein, c is 1 or 2; d is 1,2,3, 4 or 5; X is a non-nucleophilic anion,for example, PF₆ ⁻, AsF₆ ⁻, SbF₆ ⁻, CF₃SO₃ ⁻, C₂F₅SO₃ ⁻, n-C₃F₇SO₃ ⁻,n-C₄F₉SO₃ ⁻, n-C₆F₁₃SO₃ ⁻, or n-C₈F₁₇SO₃ ⁻; R8 is a pi-arene; and R9 isan anion of a pi-arene, such as a cyclopentadienyl anion. An example ofa pi-arene or an anion of pi-arene is found in published European patentapplication EP 94915. An additional example of a pi-arene includestoluene, xylene, ethylbenzene, cumene, methoxybenzene,methylnaphthalene, pyrene, perylene, stilbene, diphenylene oxide,diphenylene sulfide, or any combination thereof. In a particularexample, the pi-arene is cumene, methylnaphthalene, or stilbene.

An example of a nonnucleophilic anion X− includes FSO₃ ⁻, an anion of anorganic sulfonric acid or of a carboxylic acid; or an anion LQ_(m) ⁻, asdefined above. In particular, an anion may be derived from a partiallyfluoro or perfluoroaliphatic or a partially fluoro or a perfluoroaromatic carboxylic acid, or in particular, from a partially fluoro orperfluoroaliphatic or a partially fluoro or perfluoroaromatic organicsulfonic acid, or is an anion LQ_(m) ⁻. A further example of an anion X⁻includes BF₄ ⁻, PF₆ ⁻, AsF₆ ⁻, SbF₆ ⁻, SbF₅(OH)⁻, CF₃SO₃ ⁻, C₂F₃SO₃ ⁻,n-C₃F₇SO₃ ⁻, n-C₄F₉SO₃ ⁻, n-C₆F₁₃SO₃ ⁻, n-C₈F₁₇SO₃ ⁻, C₆F₅SO₃ ⁻,phosphorus tungstate, silicon tungstate, or any combination thereof. Inparticular, an anion is PF₆ ⁻, AsF₆ ⁻, SbF₆ ⁻, CF₃SO₃ ⁻, C₂F₃SO₃ ⁻,n-C₃F₇SO₃ ⁻, n-C₄F₉SO₃ ⁻, n-C₆F₁₃SO₃ ⁻, n-C₈F₁₇SO₃ ⁻, or any combinationthereof.

A metallocene salt can also be used in combination with an oxidizingagent. Such a combination is described in published European patentapplication EP 126712.

In a particular embodiment, the binder formulation includes from about0.1 wt % to about 20 wt %, such as about 0.2 wt % to about 10 wt %, ofcationic photoinitiator, based on the total weight of the binderformulation.

To increase the light efficiency, or to sensitize the cationicphotoinitiator to specific wavelengths, such as for example specificlaser wavelengths or a specific series of laser wavelengths, asensitizer may be used, depending on the type of initiator. An exemplarysensitizer includes a polycyclic aromatic hydrocarbon, an aromatic ketocompound, or any combination thereof. A specific example of a sensitizeris mentioned in published European patent application EP 153904. Anexemplary sensitizer includes benzoperylene,1,8-diphenyl-1,3,5,7-octatetraene, or 1,6-diphenyl-1,3,5-hexatriene, asdescribed in U.S. Pat. No. 5,667,937. An additional factor in the choiceof sensitizer is the nature and primary wavelength of the source ofactinic radiation.

In an embodiment, the binder formulation may include a radicallypolymerizable constituent. For example, the binder formulation mayinclude a compound having at least one ethylenic unsaturation which canbe polymerized with radicals. An example of a suitable ethylenicunsaturation is a group, such as acrylate, methacrylate, styrene,vinylether, vinyl ester, N-substituted acrylamide, N-vinyl amidefunctionalities, maleate ester, fumarate ester, or any combinationthereof. In particular embodiments, the ethylenic unsaturation isprovided by a group containing acrylate, methacrylate, N-vinyl, orstyrene functionality. For example, the binder formulation may includeone or more compounds having one or more (meth)acrylate functionalities.

The free-radical polymerizable acrylic material that may be used in thebinder formulation has, on average, at least one acrylic group which canbe either the free acid or an ester. By “acrylic” is meant thegroup—CH═CR1CO₂R2, where R1 can be hydrogen or methyl and R2 can behydrogen or alkyl. By “(meth)acrylate” is meant an acrylate,methacrylate, or any combination thereof. An acrylic material typicallyundergoes a polymerization or a crosslinking reaction initiated by afree radical. The acrylic material can be a monomer, an oligomer, apolymer, or any combination thereof. Typically, the acrylic material isa monomer or an oligomer.

An acrylic constituent includes, for example, diacrylate ofcycloaliphatic or aromatic diol, such as 1,4-dihydroxymethylcyclohexane,2,2-bis(4-hydroxycyclohexyl)propane, 1,4-cyclohexanedimethanol,bis(4-hydroxycyclohexyl)methane, hydroquinone, 4,4-dihydroxybiphenyl,bisphenol A, bisphenol F, bisphenol S, ethoxylated or propoxylatedbisphenol A, ethoxylated or propoxylated bisphenol F, or ethoxylated orpropoxylated bisphenol S, and any combination thereof.

A useful aromatic tri(meth)acrylate includes, for example, a reactionproduct of triglycidyl ether of trihydric phenol, or phenol or cresolnovolac having three hydroxy groups with (meth)acrylic acid. In aparticular embodiment, the acrylic material includes1,4-dihydroxymethyl-cyclohexane diacrylate, bisphenol A diacrylate,ethoxylated bisphenol A diacrylate, or any combination thereof.

In a particular embodiment, the binder formulation may include anacrylate of bisphenol A diepoxide, such as Ebecryl 3700® from UCBChemical Corporation, Smyrna, Ga., a mixed acrylate/epoxy compound ofbisphenol A such as Ebecryl 3605®, or an acrylate of1,4-cyclohexanedimethanol.

In addition to or instead of the aromatic or cycloaliphatic acrylicmaterial, other acrylic materials can be useful. A poly(meth)acrylatehaving functionality of greater than 2, where appropriate, may be usedin the binder formulation. Such a poly(meth)acrylate can be, forexample, a tri, tetra, or pentafunctional monomeric or oligomericaliphatic (meth)acrylate.

A suitable aliphatic polyfunctional (meth)acrylate includes, forexample, a triacrylate or a trimethacrylate of hexane-2,4,6-triol,glycerol, or 1,1,1-trimethylolpropane; ethoxylated or propoxylatedglycerol; or 1,1,1-trimethylolpropane or a hydroxy group-containingtri(meth)acrylate which is obtained by the reaction of triepoxycompound, such as, for example, triglycidyl ether of the mentionedtriol, with (meth)acrylic acid. In addition, pentaerythritoltetra-acrylate, bistrimethylolpropane tetra-acrylate, pentaerythritolmonohydroxytri(meth)acrylate, or dipentaerythritolmonohydroxypenta(meth)acrylate, or any combination thereof may beuseful.

In another embodiment, hexafunctional urethane (meth)acrylate is useful.Such urethane (meth)acrylate can be, for example, prepared by reacting ahydroxy-terminated polyurethane with acrylic acid or methacrylic acid,or by reacting an isocyanate-terminated prepolymer with hydroxyalkyl(meth)acrylate to follow the urethane (meth)acrylate. Also useful are anacrylate or a methacrylate, such as tris(2-hydroxyethyl)isocyanuratetriacrylate.

Typically, the amount of radically polymerizable constituent is, forexample, between about 0.1 wt % and about 60 wt %, such as between about5 wt % and about 60 wt % or between about 10 wt % and about 40 wt %.

The binder formulation may include a radical initiator, such as aradical photoinitiator, especially in combination with radicallypolymerizable constituent. A photoinitiator that forms free radicalswhen irradiated can be used. Typical a photoinitiator includes benzoin,such as benzoin; benzoin ether, such as benzoin methyl ether, benzoinethyl ether, or benzoin isopropyl ether; benzoin phenyl ether; benzoinacetate; acetophenone, such as acetophenone, 2,2-dimethoxyacetophenone,4-(phenylthio)acetophenone, or 1,1-dichloroacetophenone; benzyl; benzilketal, such as benzil dimethyl ketal, or benzil diethyl ketal;anthraquinones, such as 2-methylanthraquinone, 2-ethylanthraquinone,2-tertbutylanthraquinone, 1-chloroanthraquinone, or 2-amylanthraquinone;triphenylphosphine; benzoylphosphine oxides, such as, for example,2,4,6-trimethylbenzoyidiph-enylphosphine oxide (Lucirin TPO);benzophenone, such as benzophenone, or4,4′-bis(N,N′-dimethylamino)benzophenone; thioxanthones or xanthones;acridine derivative; phenazene derivative; quinoxaline derivative;I-phenyl-1,2-propanedione-2-O-benzoyloxime; I-aminophenyl ketones;I-hydroxyphenyl ketones, such as I-hydroxycyclohexyl phenyl ketone,phenyl(1-hydroxyisopropyl)ketone or4-isopropylphenyl(1-hydroxy-isopropyl)ketone; triazine compound, forexample, 4′″-methyl thiophenyl-1-di(trichloromethyl)-3,5-S-triazine,S-triazine-2-(stilbene)-4,6-bistrichloromethyl or paramethoxy styryltriazine, or any combination thereof.

A suitable free-radical photoinitiator alternatively includesacetophenone, such as 2,2-dialkoxybenzophenone; a 1-hydroxyphenylketone, for example 1-hydroxycyclohexyl phenyl ketone,2-hydroxy-1-{4-(2-hydroxyethoxy)phenyl}-2-methyl-1-propanone, or2-hydroxyisopropyl phenyl ketone (also called2-hydroxy-2,2-dimethylaceto-phenone), or 1-hydroxycyclohexyl phenylketone. Another class of free-radical photoinitiators comprises a benzilketal, such as, for example, benzil dimethyl ketal. Analpha-hydroxyphenyl ketone, benzil dimethyl ketal, or2,4,6-trimethylbenzoyldiphenylphosphine oxide is also useful as aphotoinitiator.

Another class of suitable free radical photoinitiators includes an ionicdye-counter ion compound, which is capable of absorbing actinic rays andproducing free radicals that can initiate the polymerization of anacrylate. As such, an ionic dye-counter ion compound can thus cure usingvisible light in an adjustable wavelength range of 400 to 700nanometers. An additional ionic dye-counter ion compound and its mode ofaction are, for example, found in European patent application EP 223587or U.S. Pat. No. 4,751,102,4,772,530 or 4,772,541. A further example ofan ionic dye-counter ion compound includes an anionic dye-iodonium ioncomplexe, an anionic dye-pyryllium ion complexe or a cationic dye-borateanion compound of the following formula:

wherein D⁺ is a cationic dye and R12, R13, R14, and R15 are, eachindependently of the others, alkyl, aryl, alkaryl, allyl, aralkyl,alkenyl, alkynyl, an alicyclic or saturated or unsaturated heterocyclicgroup. An additional example of a radical R12 to R15 can be found, forexample, in published European patent application EP 223587.

In a particular embodiment, the binder formulation may include about0.01 wt % to about 20 wt % of free-radical photoinitiator, such as about0.01 wt % to about 15 wt % of free-radical photoinitiator, based on thetotal weight of the composition.

A hydroxyl-group containing material may be used in the binderformulation. For example, the hydroxyl-group material may include liquidorganic material having a hydroxyl functionality of at least 1, andpreferably at least 2. The hydroxyl-group material may be a liquid or asolid that is soluble or dispersible in the remaining components.Typically, the material is substantially free of a group thatsubstantially slows down the curing reaction. Often, the organicmaterial contains two or more primary or secondary aliphatic hydroxylgroups (i.e., the hydroxyl group is bonded directly to a non-aromaticcarbon atom). A monomer, an oligomer, or a polymer can be useful. Thehydroxyl equivalent weight, i.e., the number average molecular weightdivided by the number of hydroxyl groups, is typically in the range of31 to 5000.

A representative example of a suitable organic material having ahydroxyl functionality of 1 includes alkanol, monoalkyl ether ofpolyoxyalkyleneglycol, monoalkyl ether of alkyleneglycol, or anycombination thereof.

A representative example of a useful monomeric polyhydroxy organicmaterial includes alkylene and arylalkylene glycol or polyol, such as1,2,4-butanetriol, 1,2,6-hexanetriol, 1,2,3-heptanetriol,2,6-dimethyl-1,2,6-hexanetriol,(2R,3R)-(−)-2-benzyloxy-1,3,4-butanetriol, 1,2,3-hexanetriol,1,2,3-butanetriol, 3-methyl-1,3,5-pentanetriol, 1,2,3-cyclohexanetriol,1,3,5-cyclohexanetriol, 3,7,11,15-tetramethyl-1,2,3-hexadecanetriol,2-hydroxymethyltetrahydropyran-3,4,5-triol,2,2,4,4-tetramethyl-1,3-cyclobutanediol, 1,3-cyclopentanediol,trans-1,2-cyclooctanediol, 1,16-hexadecanediol,3,6-dithia-1,8-octanediol, 2-butyne-1,4-diol, 1,3-propanediol,1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol,1,8-octanediol, 1,9-nonanediol, 1-phenyl-1,2-ethanediol,1,2-cyclohexanediol, 1,5-decalindiol, 2,5-dimethyl-3-hexyne-2,5-diol,2,7-dimethyl-3,5-octadiyne-2-7-diol, 2,3-butanediol,1,4-cyclohexanedimethanol, or any combination thereof.

A representative example of a useful oligomeric or polymerichydroxyl-containing material includes polyoxyethylene orpolyoxypropylene glycol or triol of molecular weights from about 200 toabout 10,000; polytetramethylene glycol of various molecular weights;copolymer containing pendant hydroxy groups formed by hydrolysis orpartial hydrolysis of a vinyl acetate copolymer, polyvinylacetal resincontaining pendant hydroxyl groups; hydroxy-terminated polyester orhydroxy-terminated polylactone; hydroxy-functionalized polyalkadiene,such as polybutadiene; aliphatic polycarbonate polyol, such as analiphatic polycarbonate diol; hydroxy-terminated polyether, or anycombination thereof.

A hydroxyl-containing monomer includes 1,4-cyclohexanedimethanol oraliphatic or cycloaliphatic monohydroxy alkanol, or any combinationthereof.

A typical hydroxyl-containing oligomer or polymer includes a hydroxyl ora hydroxyl/epoxy functionalized polybutadiene,1,4-cyclohexanedimethanol, polycaprolactone diol or triol,ethylene/butylene polyol, monohydroxyl functional monomer, or anycombination thereof. An example of polyether polyol is polypropyleneglycol of various molecular weight or glycerol propoxylate-B-ethoxylatetriol. Another example includes a linear or a branchedpolytetrahydrofuran polyether polyol available in various molecularweights, such as for example 250, 650, 1000, 2000, and 2900 MW.

In a particular embodiment, the binder formulation may include up to 60wt % of polyol. For example, the binder formulation may include about0.1 wt % to about 60 wt % polyol, such as between about 3 wt % and about20 wt %.

The binder formulation includes a latent coloring component. In aparticular embodiment, the latent coloring component forms a chromophorein response to curing of polymer constituent. In an exemplaryembodiment, the latent coloring component forms color or changes coloron contact with a photochemically generated photoacid. In a particularembodiment, the latent coloring component is a triaryl methane-,diphenyl methane-thiazine-, spiro-, lactam-, fluoran orisobenzofuranone-based color former. An example of triarylmethane-basedcolor former includes3-3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide,3,3-bis(p-dimethylaminophenyl)phthalide,3-(p-dimethylaminophenyl)-3-(1,2-dimethylindole-3-yl)phthalide,3-(p-dimethylaminophenyl)-3-(2-methylindole-3-yl)phthalide,3,3-bis(1,2-dimethylindole-3-yl)-5-dimethylaminophthalide,3,3-bis(1,2-dimethylindole-3-yl)-6-dimethylaminophthalide,3,3-bis(9-ethylcarbazole-3-yl)-6-dimethylaminophthalide,3,3-bis(2-phenylindole-3-yl)-6-dimethylaminophthalide,3-p-dimethylaminophenyl-3-(1-methylpyrrole-3-yl)-6-dimethylaminophthalide,etc., or triphenyl methane e.g., Crystal Violet Lactone, or anycombination thereof.

A typical diphenylmethane-based latent colorant component includes4,4′-bis-dimethylaminobenzhydryl benzyl ether,N-halophenyl-leucoauramine, N-2,4,5-trichlorophenyl-leucoauramine, orany combination thereof. An exemplary thiazine-based color formerincludes benzoyl-leucomethylene blue, p-nitrobenzoyl-leucomethyleneblue, or any combination thereof. An exemplary spiro-based color formerincludes 3-methyl-spiro-dinaphthopyran, 3-ethyl-spiro-dinaphthopyran,3-phenyl-spirodinapthopyran, 3-benzyl-spiro-dinaphthopyran,3-methyl-naphtho-(6′-methoxybenzo)spiropyran,3-propyl-spiro-dibenzopyran, or any combination thereof. A lactam-basedcolor former includes rhodamine-b-anilinolactam,rhodamine-(p-nitroanilino) lactam, rhodamine-(o-chloroanilino)lactam, orany combination thereof. A fluoran-based color former includes3,6-dimethoxyfluoran, 3,6-diethoxyfluoran, 3,6-dibutoxyfluoran,3-dimethylamino-7-methoxyfluoran, 3-dimethylamino-6-methoxylfluoran,3-dimethylamino-7-methoxyfluoran, 3-diethylamino-7-chlorofluoran,3-diethylamino-6-methyl-7-chlorofluoran,3-diethylamino-6,7-dimethylfuoran,3-(N-ethyl-p-toluidino)-7-methylfluoran,3-diethylamino-7-(N-acetyl-N-methylamino)fluoran,3-diethylamino-7-N-methylaminofluoran,3-diethylamino-7-dibenzylaminofluoran,3-diethylamino-5-methyl-7-dibenzylaminofluoran,3-diethylamino-7-(N-methyl-N-benzylamino)fluoran,3-diethylamino-7-(N-chl-oroethyl-N-methylamino)fluoran,3-diethylamino-7-diethylaminofluoran,3-(N-ethyl-p-toluidino)-6-methyl-7-phenylaminofluoran,3-(N-ethyl-p-toluidino)-6-methyl-7-phenylaminofluoran,3-diethylamino-7-(2-carbomethoxy-phenylamino)fluoran,3-(N-ethyl-N-isoamylamino)-6-methyl-7-phenylaminofluoran,3-(N-cyclohexyl-N-methylamino)-6-methyl-7-phenylaminofluoran,3-pyrrolidino-6-methyl-7-phenylaminofluoran,3-piperidino-6-methyl-7-phenylaminofluoran,3-diethylamino-6-methyl-7-xylidinofluoran,3-diethylamino-7-(o-chlorophenylamino)fluoran,3-dibutylamino-7-(o-chloro-phenylamino)fluoran,3-pyrrolidino-6-methyl-7-p-butylphenylaminofluoran, or any combinationthereof.

Latent colorant components permitting the production of a wide range ofcolors are described, for example, by Peter Gregory in High-TechnologyApplications of Organic Colourants, Plenum Press, pages 124-134.

In particular, a latent coloring component includes anisobenzofuranone-based color former or a color former that is availableunder the tradenames of Copikem and Pergascript. An example of such acoloring component inlcudes Copikem 20(3,3-Bis(1-butyl-2-methyl-H-indol-3-yl)-1-(3H)-isobenzofuranone),Copikem 5 (2′-Di(phenylmethy)amino-6′-(diethylamino)spiro(isobenzofuran-1 (3H),9′-(9H)xanthem)-3-one), Copikem 14 (a substituted phthalide), Copikem 7(3-{(4Dimethylamino)-phenyl}-3-(1-butyl-2methylindol-3yl)-6-dimethyamino)-1-(3H)-isobenzofuranone),Copikem 37(2-(2-Octoxyphenyl)-4-(4-dimethylaminophenyl)-6-(phenyl)pyridine),Pergascript Black I-R(6″-(Dimethylamino)-3″-methyl-2″-(phenylamino)spiro-(isobenzofuran-1(3H),9″(9H)xanthem-3-one), or Pergascript Color Former (like diamiofluorancompound, bisaryl carbazolyl methane compound, phthalide compound,bisindolyl phthalide compound, aminofluoran compound, or quinazolinecompound), or any combination thereof. While the above examples arepresented for illustrative purposes, use of various other exemplarycolorants can be envisaged based on the disclosure herein.

In general, the latent colorant or latent coloring component may reactwith or change color in response to byproducts or chemical changesassociated with curing of the binder formulation. For example, thelatent colorant may change color in response to activation of a cationicphotoinitiator. In another example, the latent colorant may change colorin response to a concentration of photoacid. In a further example, thelatent colorant may change color in response to changes in concentrationof monomeric constituents, solvents, or byproducts of the polymerizationof monomers. In an additional example, the latent colorant may changecolor in response to generation of cations or the concentration ofcations, in particular, cations, such as H⁺ cations, which may beexpressed as pH in particular binder formulations and solvents.

In a particular embodiment, the binder formulation includes betweenabout 0.0001 wt % and about 2.0 wt %, such as about 0.0005 wt % to about1.0 wt %, latent coloring component.

The binder formulation may also include a filler. In an embodiment, aninorganic substance is used and provided for water-resistingcapabilities and mechanical properties. An example of an inorganicfiller includes silica, glass powder, alumina, alumina hydrate,magnesium oxide, magnesium hydroxide, barium sulfate, calcium sulfate,calcium carbonate, magnesium carbonate, silicate mineral, diatomaceousearth, silica sand, silica powder, titanium oxide, aluminum powder,bronze, zinc powder, copper powder, lead powder, gold powder, silverdust, glass fiber, titanic acid potassium whiskers, carbon whiskers,sapphire whiskers, verification rear whiskers, boron carbide whiskers,silicon carbide whiskers, silicon nitride whiskers, or any combinationthereof.

The condition of the surface of the particles of the filler used and theimpurities contained in filler from the manufacturing process can affectthe curing reaction of the resin composition. In such a case, the fillerparticles may be washed with an appropriate primer.

The inorganic filler also may be surface-treated with a silane couplingagent. An exemplary silane coupling agent includes vinyl triclorosilane,vinyl tris(β-methoxyethoxy) silane, vinyltriethoxy silane,vinyltrimethoxy silane, r-(methacryloxypropyl)trimethoxy silane,β-(3,4-epoxycyclohexyl)ethyltrimethoxy silane,r-glycydoxypropyltrimethoxy silane, r-glycydoxypropylmethyl diethoxysilane, N-β-(aminoethyl)-r-aminopropyltrimethoxy silane,N-β-(aminoethyl)-.gamma.-aminopropylmethyldimethoxy silane,r-aminopropyltriethoxysilane, N-phenyl-r-amino propyl trimethoxy silane,r-mercaptopropyl trimethoxysilane, and r-chloropropyltrimethoxy silane,or any combination thereof.

The above inorganic filler may be used singly or in combination of twoor more. In a particular embodiment, the binder formulation includesabout 0.01 wt % to about 95 wt % filler relative to the total weight ofthe composition. For example, the binder may include about 10 wt % toabout 90 wt %, or about 20 wt % to about 80 wt % filler.

In a further particular embodiment, the particulate filler may be formedof inorganic particles, such as, for example, metals (such as, forexample, steel, Au or Ag) or a metal complex, such as, for example,metal oxide, metal hydroxide, metal sulfide, metal halogen complex,metal carbide, metal phosphate, inorganic salt (like, for example,CaCO₃), ceramics, or any combination thereof. An example of a metaloxide includes ZnO, CdO, SiO₂, TiO₂, ZrO₂, CeO₂, SnO₂, MoO₃, WO₃, Al₂O₃,In₂O₃, La₂O₃, Fe₂O₃, CuO, Ta₂O₅, Sb₂O₃, Sb₂O₅, or any combinationthereof. A mixed oxide containing different metals may also be present.The nanoparticle, for example, may comprise a particle selected from thegroup consisting of ZnO, SiO₂, TiO₂, ZrO₂, SnO₂, Al₂O₃, co-formed silicaalumina, or any combination thereof. The nanometer sized particle mayalso have an organic component, such as, for example, carbon black,highly crosslinked/core shell polymer nanoparticle, or an organicallymodified nanometer-size particle, or any combination thereof. Such afiller is described in, for example, U.S. Pat. No. 6,467,897 and WO98/51747, hereby incorporated by reference.

Particulate filler formed via a solution-based processes, such assol-formed or a sol-gel formed ceramic, are particularly well suited foruse in the composite binder. A suitable sol is commercially available.For example, a colloidal silica in aqueous solution is commerciallyavailable under such trade designations as “LUDOX” (E.I. DuPont deNemours and Co., Inc. Wilmington, Del.), “NYACOL” (Nyacol Co., Ashland,Ma.) or “NALCO” (Nalco Chemical Co., Oak Brook, Ill.). Many commerciallyavailable sols are basic, being stabilized by alkali, such as sodiumhydroxide, potassium hydroxide, or ammonium hydroxide. An additionalexample of a suitable colloidal silica is described in U.S. Pat. No.5,126,394, incorporated herein by reference. A well-suited particleincludes sol-formed silica and sol-formed alumina. The sol can befunctionalized by reacting one or more appropriate surface-treatmentagents with the inorganic oxide substrate particle in the sol.

In a particular embodiment, the particulate filler is sub-micron sized.For example, the particulate filler may be a nano-sized particulatefiller, such as a particulate filler having an average particle sizeabout 3 to 500 nm. In an exemplary embodiment, the particulate fillerhas an average particle size about 3 nm to about 200 nm, such as about 3nm to about 100 nm, about 3 nm to about 50 nm, about 8 nm to about 30nm, or about 10 nm to about 25 nm. In a particular embodiment, theaverage particle size is not greater than about 500 nm, such as notgreater than about 200 nm, less than about 100 nm, or not greater thanabout 50 nm. For the particulate filler, the average particle size maybe defined as the particle size corresponding to the peak volumefraction in a small-angle neutron scattering (SANS) distribution curveor the particle size corresponding to 0.5 cumulative volume fraction ofthe SANS distribution curve.

The particulate filler may also be characterized by a narrowdistribution curve having a half-width not greater than about 2.0 timesthe average particle size. For example, the half-width may be notgreater than about 1.5 or not greater than about 1.0. The half-width ofthe distribution is the width of the distribution curve at half itsmaximum height, such as half of the particle fraction at thedistribution curve peak. In one particular embodiment, the particle sizedistribution curve is mono-modal.

The particulate filler is generally dispersed in an external phase.Prior to curing, the particulate filler is colloidally dispersed withinthe binder formulation and forms a colloidal composite binder oncecured. For example, the particulate material may be dispersed such thatBrownian motion sustains the particulate filler in suspension. Ingeneral, the particulate filler is substantially free of particulateagglomerates. For example, the particulate filler may be substantiallymono-disperse such that the particulate filler is dispersed as singleparticles, and in particular examples, has only insignificantparticulate agglomeration, if any.

In a particular embodiment, the particles of the particulate filler aresubstantially spherical. Alternatively, the particles may have a primaryaspect ratio greater than 1, such as at least about 2, at least about 3,or at least about 6, wherein the primary aspect ratio is the ratio ofthe longest dimension to the smallest dimension. The particles may alsobe characterized by a secondary aspect ratio defined as the ratio oforthogonal dimensions in a plane generally perpendicular to the longestdimension. The particles may be needle-shaped, such as having a primaryaspect ratio at least about 2 and a secondary aspect ratio not greaterthan about 2, such as about 1. Alternatively, the particles may beplatelet-shaped, such as having a primary aspect ratio at least about 2and a secondary aspect ratio at least about 2.

In a particular embodiment, the particulate filler is prepared in anaqueous solution and mixed with the external phase of a suspension. Theprocess for preparing such suspension includes introducing an aqueoussolution, such as an aqueous silica solution; polycondensing thesilicate, such as to a particle size of 3 nm to 50 nm; adjusting theresulting silica sol to an alkaline pH; optionally concentrating thesol; mixing the sol with constituents of the external fluid phase of thesuspension; and optionally removing water or other solvent constituentsfrom the suspension. For example, an aqueous silicate solution isintroduced, such as an alkali metal silicate solution (e.g. a sodiumsilicate or potassium silicate solution) with a concentration in therange between 20% and 50% by weight based on the weight of the solution.The silicate is then polycondensed to a particle size of from 3 nm to 50nm, for example, by treating the alkali metal silicate solution withacidic ion exchangers. The resulting silica sol is adjusted to analkaline pH (e.g. pH>8) to stabilized against further polycondensationor agglomeration of existing particles. Optionally, the sol can beconcentrated, for example, by distillation, typically to SiO₂concentration of about 30% to about 40% by weight. The sol is mixed withconstituents of the external fluid phase. Thereafter, water or othersolvent constituents are removed from the suspension. In a particularembodiment, the suspension is substantially water-free.

The fraction of the non-filler constituents in the pre-cured binderformulation, generally including the organic polymeric constituents, asa proportion of the binder formulation can be about 20% to about 95% byweight, for example, about 30% to about 95% by weight, and typicallyfrom about 50% to about 95% by weight, and even more typically fromabout 55% to about 80% by weight. The fraction of the dispersedparticulate filler phase can be about 5% to about 80% by weight, forexample, about 5% to about 70% by weight, typically from about 5% toabout 50% by weight, and more typically from about 20% to about 45% byweight. The colloidally dispersed and submicron particulate fillersdescribed above are particularly useful in concentrations at least about5 wt %, such as at least about 10 wt %, at least about 15 wt %, at leastabout 20 wt %, or as great as 40 wt % or higher. In contrast withtraditional fillers, the solution formed nanocomposites exhibit lowviscosity and improved processing characteristics at higher loading. Theamounts of components are expressed as weight % of the componentrelative to the total weight of the composite binder formulation, unlessexplicitly stated otherwise.

The binder formulation including an external phase comprising polymericor monomeric constituents and optionally including dispersed particulatefiller may be used to form a make coat, size coat, compliant coat, orback coat of a coated abrasive article. In a exemplary process forforming a make coat, the binder formulation is coated on a backing,abrasive grains are applied over the make coat, and the make coat iscured. A size coat may be applied over the make coat and abrasivegrains. In another exemplary embodiment, the binder formulation isblended with the abrasive grains to form abrasive slurry that is coatedon a backing and cured. Alternatively, the abrasive slurry is applied toa mold, such as injected into a mold and cured to form a bonded abrasivearticle.

The abrasive grains may be formed of any one of or a combination ofabrasive grains, including silica, alumina (fused or sintered),zirconia, zirconia/alumina oxide, silicon carbide, garnet, diamond,cubic boron nitride, silicon nitride, ceria, titanium dioxide, titaniumdiboride, boron carbide, tin oxide, tungsten carbide, titanium carbide,iron oxide, chromia, flint, emery, or any combination thereof. Forexample, the abrasive grains may be selected from a group consisting ofsilica, alumina, zirconia, silicon carbide, silicon nitride, boronnitride, garnet, diamond, cofused alumina zirconia, ceria, titaniumdiboride, boron carbide, flint, emery, alumina nitride, or a blendthereof. Particular embodiments have been created by use of denseabrasive grains comprised principally of alpha-alumina.

The abrasive grain may also have a particular shape. Examples of suchshapes include rods, triangles, pyramids, cones, solid spheres, hollowspheres and the like. Alternatively, the abrasive grain may be randomlyshaped.

The abrasive grains generally have an average grain size not greaterthan 2000 microns, such as not greater than about 1500 microns. Inanother example, the abrasive grain size is not greater than about 750microns, such as not greater than about 350 microns. For example, theabrasive grain size may be at least 0.1 microns, such as from about 0.1microns to about 1500 micron, and more typically from about 0.1 micronsto about 200 microns or from about 1 micron to about 100 microns. Thegrain size of the abrasive grains is typically specified to be thelongest dimension of the abrasive grain. Generally, there is a rangedistribution of grain sizes. In some instances, the grain sizedistribution is tightly controlled.

In a blended abrasive slurry including the abrasive grains and thebinder formulation, the abrasive grains provide from about 10% to about90%, such as from about 30% to about 80%, of the weight of the abrasiveslurry.

The abrasive slurry may further include a grinding aid to increase thegrinding efficiency and cut rate. Useful grinding aids can be inorganicbased, such as halide salts, for example sodium cryolite, potassiumtetrafluoroborate, etc.; or organic based, such as chlorinated waxes,for example, polyvinyl chloride. A particular embodiment includescryolite and potassium tetrafluoroborate with particle size ranging from1 micron to 80 microns, and most typically from 5 microns to 30 microns.The weight percent of grinding aid ranges is generally not greater thanabout 50 wt %, such as from about 0 wt % to about 50 wt %, and mosttypically from about 10 wt % to about 30 wt % of the entire slurry(including the abrasive grains).

FIG. 1 illustrates an exemplary embodiment of a coated abrasive article100, which includes abrasive grains 106 secured to a backing or supportmember 102. Generally, the abrasive grains 106 are secured to thebacking 102 by a make coat 104. The make coat 104 includes a binder,which is typically formed of a cured binder formulation including latentcolorant. When the binder formulation is cured the latent colorantreacts to form reaction activated chromophores that impart color to thebinder or change the color of the binder.

The coated abrasive article 100 may further include a size coat 108overlying the make coat 104 and the abrasive grains 106. The size coat108 generally functions to further secure the abrasive grains 106 to thebacking 102 and may also provide grinding aids. The size coat 108 isgenerally formed from a cured binder formulation that may be the same ordifferent from the make coat binder formulation and may include a secondlatent colorant.

The coated abrasive 100 may also, optionally, include a back coat 112.The back coat 112 functions as an anti-static layer, preventing abrasivegrains from adhering to the back side of the backing 102 and preventingswarf from accumulating charge during sanding. In another example, theback coat 112 may provide additional strength to the backing 102 and mayact to protect the backing 102 from environmental exposure. In anotherexample, the back coat 112 can also act as a compliant layer. Thecompliant layer may act to relieve stress between the make coat 104 andthe backing 102.

The backing may be flexible or rigid. The backing may be made of anynumber of various materials including those conventionally used asbackings in the manufacture of coated abrasives. An exemplary flexiblebacking includes a polymeric film (including primed film), such aspolyolefin film (e.g., polypropylene including biaxially orientedpolypropylene), polyester film (e.g., polyethylene terephthalate),polyamide film, cellulose ester film, metal foil, mesh, foam (e.g.,natural sponge material or polyurethane foam), cloth (e.g., cloth madefrom fibers or yarns comprising polyester, nylon, silk, cotton,poly-cotton or rayon), paper, vulcanized paper, vulcanized rubber,vulcanized fiber, nonwoven materials, any combination thereof, or anytreated version thereof. A cloth backing may be woven or stitch bonded.In a particular example, the backing is selected from a group consistingof paper, polymer film, cloth, cotton, poly-cotton, rayon, polyester,poly-nylon, vulcanized rubber, vulcanized fiber, metal foil, or anycombination thereof. In another example, the backing includespolypropylene film or polyethylene terephthalate (PET) film.

The backing may, optionally, have at least one of a saturant, a presizelayer or a backsize layer. The purpose of these layers is typically toseal the backing or to protect yarn or fibers in the backing. If thebacking is a cloth material, at least one of these layers is typicallyused. The addition of the presize layer or backsize layer mayadditionally result in a “smoother” surface on either the front or theback side of the backing. Other optional layers known in the art mayalso be used (e.g., tie layer; see, e.g., U.S. Pat. No. 5,700,302(Stoetzel et al.), the disclosure of which is incorporated byreference).

An antistatic material may be included in any of the above clothtreatment materials. The addition of an antistatic material can reducethe tendency of the coated abrasive article to accumulate staticelectricity when sanding wood or wood-like material. Additional detailsregarding antistatic backings and backing treatments can be found in,for example, U.S. Pat. No. 5,108,463 (Buchanan et al.); U.S. Pat. No.5,137,542 (Buchanan et al.); U.S. Pat. No. 5,328,716 (Buchanan); andU.S. Pat. No. 5,560,753 (Buchanan et al.), the disclosures of which areincorporated herein by reference.

The backing may be a fibrous reinforced thermoplastic, such asdescribed, for example, in U.S. Pat. No. 5,417,726 (Stout et al.), or anendless spliceless belt, as described, for example, in U.S. Pat. No.5,573,619 (Benedict et al.), the disclosures of which are incorporatedherein by reference. Likewise, the backing may be a polymeric substratehaving hooking stems projecting therefrom, such as that described, forexample, in U.S. Pat. No. 5,505,747 (Chesley et al.), the disclosure ofwhich is incorporated herein by reference. Similarly, the backing may bea loop fabric, such as that described, for example, in U.S. Pat. No.5,565,011 (Follett et al.), the disclosure of which is incorporatedherein by reference.

In some examples, a pressure-sensitive adhesive is incorporated onto theback side of the coated abrasive article such that the resulting coatedabrasive article can be secured to a pad. Exemplary pressure-sensitiveadhesives include latex crepe, rosin, acrylic polymer or copolymer,including polyacrylate ester (e.g., poly(butyl acrylate)), vinyl ether(e.g., poly(vinyl n-butyl ether)), alkyd adhesive, rubber adhesives(e.g., natural rubber, synthetic rubber, chlorinated rubber), or anymixture thereof.

An exemplary rigid backing includes a metal plate, a ceramic plate, orthe like. Another example of a suitable rigid backing is described, forexample, in U.S. Pat. No. 5,417,726 (Stout et al.), the disclosure ofwhich is incorporated herein by reference.

A coated abrasive article, such as the coated abrasive article 100 ofFIG. 1, may be formed by coating a backing with a binder formulation orabrasive slurry. Optionally, the backing may be coated with a compliantcoat or back coat prior to coating with the make coat. Typically, thebinder formulation is applied to the backing to form the make coat. Inan embodiment, abrasive grains are applied with the binder formulation,wherein the abrasive grains are blended with the binder formulation toform abrasive slurry prior to application to the backing. Alternatively,the binder formulation is applied to the backing to form the make coatand the abrasive grains are applied to the make coat, such as throughelectrostatic and pneumatic methods. The binder formulation is curedsuch as through thermal methods or exposure to actinic radiation,causing a color change in the latent colorant.

Optionally, a size coat is applied over the make coat and abrasivegrains. The size coat may be applied prior to curing the make coat, themake coat and size coat being cured simultaneously. Alternatively, themake coat is cured prior to application of the size coat and the sizecoat is cured separately. Latent colorants in the size coat may changecolor during curing.

The binder formulation forming the make coat, the size coat, thecompliant coat or the back coat may include colloidal binderformulation. The colloidal binder formulation may include sub-micronparticulate filler, such as nano-sized particulate filler having anarrow particle size distribution. In a particular embodiment, thecolloidal binder formulation is cured to form the size coat. In anotherembodiment, the colloidal binder formulation is cured to form the makecoat. Alternatively, the colloidal binder formulation may be cured toform the optional compliant coat or the optional back coat.

In a particular embodiment, the coats and abrasive grains may bepatterned to form structures. For example, the make coat may bepatterned to form surface structures that enhance abrasive articleperformance. Patterns may be pressed or rolled into the coats using, forexample, a rotogravure apparatus to form a structured or engineeredabrasive article.

An exemplary embodiment of an engineered or structured abrasive isillustrated in FIG. 2. The structured abrasive includes a backing 202and a layer 204 including abrasive grains. The backing 202 may be formedof the materials described above in relation to the backing 102 ofFIG. 1. Generally, the layer 204 is patterned to have surface structures206.

The layer 204 may be formed as one or more coats. For example, the layer204 may include a make coat and optionally, a size coat. The layer 204generally includes abrasive grains and a binder. In one exemplaryembodiment, the abrasive grains are blended with a binder formulation toform an abrasive slurry. Alternatively, the abrasive grains are appliedto the binder after the binder is coated on the backing 202. Optionally,a functional powder may be applied over the layer 204 to prevent thelayer 204 from sticking to the patterning tooling. The binder of themake coat or the size coat may include latent colorant. The structuredabrasive article 200 optionally may include compliant and back coats(not shown). These coats may function as described above.

In a further example, a binder formulation including latent colorant maybe used to form bonded abrasive articles, such as the abrasive article300 illustrated in FIG. 3. In a particular embodiment, binderformulation and abrasive grains are blended to form abrasive slurry. Theabrasive slurry is applied to a mold and the binder formulation iscured, causing a change in color of the latent colorant. The resultingabrasive article, such as article 300, includes the abrasive grainsbound by nano-composite binder in a desired shape.

In a particular embodiment, the abrasive article is formed by blendingnanocomposite precursors with other polymeric precursors andconstituents. For example, a nanocomposite epoxy precursor, includingnano-sized particulate filler and epoxy precursor, is mixed with acrylicprecursor to form a nanocomposite binder formulation. The binderformulation is applied to a substrate, such as a backing or to a mold.Abrasive grains are also applied to the substrate and the binderformulation is cured.

When the nanocomposite binder forms a make coat for a coated abrasivearticle, the nanocomposite binder formulation may be applied to abacking and abrasive grains applied over the formulation. Alternatively,the binder formulation may be applied over the abrasive grains to form asize coat. In another example, the binder formulation and the abrasivegrains may be blended and applied simultaneously to form a make coatover a substrate or to fill a mold. Generally, the binder formulationmay be cured using thermal energy or actinic radiation, such asultraviolet radiation.

In a particular embodiment, the binder formulation includes an epoxyconstituent, a cationic photoinitiator within the epoxy constituent, anda latent colorant configured to change color in response to activationof the cationic photoiniator. The binder formulation may include about10 wt % to about 90 wt %, such as about 65 wt % to about 80 wt %, of theepoxy constituent and may include about 0.1 wt % to about 20 wt %, suchas about 0.1 wt % to about 4.0 wt %, of the cationic photoinitiator. Theepoxy constituent may include nano-sized particulate filler, such asfiller having particle size not greater than about 100 nm, such as notgreater than about 50 nm.

The binder formulation may include an acrylic constituent and a radicalgenerating photoinitiator. The binder formulation may include about 0.1wt % to about 60 wt %, such as about 5 wt % to about 15 wt %, of theacrylic constituent and may include about 0.01 wt % to about 20 wt %,such as about 0.1 wt % to about 4 wt %, radical generatingphotoinitiator. The acrylic constituent may include nano-sizedparticulate filler, such as filler having particle size not greater thanabout 100 nm, such as not greater than about 50 nm. The binderformulation may also include a polyol constituent in an amount of about0.1 wt % to about 60 wt %, such as about 10 wt % to about 17 wt %.

The latent colorant may exhibit a specific color based on curing of theepoxy constituent. In an example, the latent colorant reacts withbyproducts of the cationic photoinitiator to change color. The binderformulation may include one or more colorants. For example, the binderformulation may further include a second latent colorant. The secondlatent colorant may change to a second color based on the curing. Inanother example, the second colorant changes color in response to adifferent reaction, such as activation of a radical generatingphotoinitiator.

In an exemplary embodiment, the latent colorant and the second latentcolorant may together change to appear as a desirable color. Forexample, a first reaction activated chromophore associated with thefirst latent colorant may have a first electromagnetic energy absorptionprofile and a second reaction activated chromophore associated with thesecond latent colorant may have a second electromagnetic energyabsorption profile. In an example, the first electromagnetic energyabsorption profile is different from the second electromagnetic energyabsorption profile. In a further example, the first electromagneticenergy absorption profile and the second electromagnetic energyabsorption profile appear as a desired color.

In an alternative embodiment, a latent colorant may be selected foraddition to a binder formulation to provide color coding of binderformulations. For example, a first binder formulation may include afirst latent colorant and a second binder formulation may include asecond latent colorant. In such an embodiment, the color of a curedabrasive product may aid in identifying the binder formulation used toform the cured abrasive product. In a further example, each coat, suchas a make coat or a size coat, may be formed from a different binderformulation and each of the different binder formulations may include adifferent latent colorant.

The binder formulation may be cured to form an abrasive product, such asa layer of a coated abrasive product. Latent colorants becomechromophores through reactions associated with curing of the polymercomponents. Generally, the latent colorants and chromophores areorganic, not to be confused with inorganic pigments. Typically, thebinder formulation and resulting abrasive product are free ofparticulate pigment. In some examples, particulate pigment can interferewith curing through actinic radiation, causing defects in resultingabrasive products.

In another embodiment, the disclosure is directed to a method ofmanufacturing an abrasive article. The method includes initiating acuring process on a workpiece, determining a target color exhibited bythe workpiece, and terminating the curing process based on the targetcolor. The target color may represent partial curing or full curing. Thecuring process may include photo curing or thermal curing. In anexample, a make coat is applied to the abrasive article workpiece priorto curing. In another example, an uncured size coat is applied to theworkpiece prior to curing. In a further example, a mold is filled toform the workpiece. A second curing process may be initiated afterterminating the curing process, a second target color may be determinedand the second curing process terminated based on the second targetcolor.

In a further exemplary embodiment, the disclosure is directed to amethod of controlling abrasive product quality. The method includesforming an abrasive product having a polymer matrix and a reactionactivated chromophore, inspecting the abrasive product for a colorcharacteristic, and categorizing the abrasive product based on the colorcharacteristic. The color characteristic may, for example, be a targetcolor or color uniformity. Categorizing the abrasive product may includerejecting the abrasive product, accepting the abrasive product orgrading the abrasive product. Grades may be associated with abrasiveproduct usage conditions. The product may be further cured aftercategorizing.

Measurement of color can be performed with a chromameter. When the resincomposition is opaque, for example, due to the presence of a filler, thecolor of the resin and the article is measured with a chromameter on thearticle or resin. In an example, a chromameter provides three values inthe L*a*b color scale (CIELAB). The CIELAB color scale is an approximateuniform color scale. In a uniform color scale, the differences betweenpoints plotted in the color space correspond to visual differencesbetween the colors plotted. The CIELAB color space is organized in acube form. The L* axis runs from the top to bottom. The maximum L* is100, which represents a reflecting diffuser. The minimum L* is zero,which represents black. The a* and b* axis have no specific numericallimit. Positive a* is typically red and negative a* is typically green.Positive b* is generally yellow and negative b* is generally blue. Forexample, when a* is −60, it represents green and when a* is +60, itrepresents red. The b* represents blue when it is −60 and yellow when itis +60. Articles having a* and b* value between −20 and 20 typicallyhave a grey appearance. Articles having a* and b* values between −20 and−60 or between 20 and 60 are generally more colorful.

Typically, conventional resin compositions with and without fillers butwithout latent colorant exhibit large L* values of between 90 and 100.In contrast, embodiments of articles, for example, formed by UV-curingof a resin including latent colorant exhibit a different color than theuncured resin. Such a color may be expressed as a change in L* value, a*value, or b* value relative to the resin. In an example, the L* valuemay change at least about 10 units, such as at least about 20 units.Typically, the a* or b* values of an article change by at least about 10units after cure of the resin. For instance, the a* or b* value maychange by at least about 20 units. In an exemplary embodiment, the L*value may not change substantially, but the color may change, forexample, from red to blue. In such an embodiment, the a* or b* value maychange at least about 20 units, such as at least about 30 units. Inanother embodiment, the L* value of the article changes relative to theresin, so that cured articles have L* values of between 0 and 85, suchas between 20 and 75. In an example, the a* or b* value of the curedarticles may stay the same as the values of the resin when the L* valuechanges.

In a particular embodiment, the L* value of a binder formulation or anabrasive article workpiece may change by at least about 10%, such as atleast about 20% or at least about 30%. In another example, the a* valueor the b* value may change by at least about 10%, such as at least about20% or at least about 30%. When determining a target color, the methodmay include determining a target L* value or a change in L* value.Alternatively, the method may include determining a target a* value or atarget b* value or changes in the a* value or the b* value.

EXAMPLE 1

An example binder formulation includes: INGREDIENT Wt. % DescriptionNanopox XP 22/0314 72.02 Epoxy 4,8-bis(hydroxymethyl) 14.40 Polyoltricyclo[5.2.1.0)decane Chivacure 184 0.48 Photoinitiator Chivacure 11762.88 Photoinitiator Nanocryl XP 21/0954 9.60 Acrylate Specialty Blue 10.40 additive BYK A-501 0.02 additive Silwet L 7600 0.20 additiveTotals: 100.00

EXAMPLE 2

Sample binder formulations are prepared and cured. The color of thecured samples are tested using a HunterLab Color Quest XE chromameter inreflectance test mode with a D65 illuminant and at an angle of 10°. Thecolor of the samples is represented in the CIELAB color scale. A whitebacking medium is used during measurement.

Effect of dye concentration on binder color is determined by testingbinder formulations in a standardized abrasive article configuration (4inch length and 10 inch width). The binder formulations at different dyeconcentrations are used as a size coat over abrasive grains and a makecoat. Film samples that have size coatings at different dyeconcentration are UV cured at 300 W D bulb/600 W H bulb at a line speed50 feet/minute. The abrasive grains are 80 micron heat-treatedsemi-friable aluminum oxide from Treibacher (BFRPL) P180 grit and themake coat is formed of UV-curable epoxy/acrylate resins. The abrasivegrains and make coat overlie a polyester backing. The effect of dyeconcentration on the value L*, a*, b* is determined. Size coats onsample abrasive articles are formed from binder formulations includingNanopox XP A610 available from Hanse Chemie, an epoxy resin including3,4-epoxy cyclohexyl methyl-3,4-epoxy cyclohexyl carboxylate and 40 wt %colloidal silica particulate filler. The binder formulations alsoinclude UVR 6105, which includes 3,4-epoxy cyclohexyl methyl-3,4-epoxycyclohexyl carboxylate and no particulate filler. The binderformulations further include a polyol (4,8-bis(hydroxymethyl)tricyclo(5.2.1.0)decane), a cationic photoinitiator (Chivacure 1176), aradical photoinitiator (Irgacure 2022, available from Ciba®), acrylateprecursor (SR 399, a dipentaerythritol pentaacrylate available fromAtofina-Sartomer, Exton, Pa.), and dye (specialty blue 1, available fromNoveon Hilton Davis, Inc., 2235 Langdon Farms Rd., Cincinnati, Ohio45237-4790).

Table 1 illustrates the concentration of components in the binderformulations and the resulting value of L*, a*, and b*. Generally,increasing the concentration of Specialty Blue 1 dye causes a reductionin L* for the cured binder formulation. In addition, b* changes in anegative direction with increasing Specialty Blue 1 dye in the binderformulation. TABLE 1 INGREDIENT A B C D Nanopox A610 60.00 60.00 60.0060.00 UVR 6105 19.92 19.92 19.92 19.92 4,8-bis(hydroxymethyl) 13.5013.50 13.50 13.50 tricyclo(5.2.1.0)decane Irgacure 2022 0.48 0.48 0.480.48 Chivacure 1176 1.50 1.50 1.50 1.50 SR 399 4.60 4.60 4.60 4.60Specialty Blue 1 0 0.1 0.2 0.4 L* 72.05 61.61 52.61 44.58 a* −0.76 −7.52−7.75 −2.36 b* 4.16 −10.96 −22.19 −30.11

Exemplary embodiments of the above described binder formulations andabrasive articles formed from the binder formulation may advantageouslybe useful in quality control, end product coloration, characterizationof the product, and process control. Absence of particulate pigmentsadvantageously leads to improved curing for actinic radiation curablebinder formulations.

The above-disclosed subject matter is to be considered illustrative, andnot restrictive, and the appended claims are intended to cover all suchmodifications, enhancements, and other embodiments, which fall withinthe true scope of the present invention. Thus, to the maximum extentallowed by law, the scope of the present invention is to be determinedby the broadest permissible interpretation of the following claims andtheir equivalents, and shall not be restricted or limited by theforegoing detailed description.

1. An abrasive article having a layer comprising: an epoxy constituent;a cationic photointiator within the epoxy constituent; and a latentcolorant configured to change color in response to activation of thecationic photoinitiator.
 2. The abrasive article of claim 1, furthercomprising an acrylic constituent and a radical generatingphotoinitiator.
 3. The abrasive article of claim 2, wherein the layercomprises about 0.1 wt % to about 60 wt % of the acrylic constituent.4-7. (canceled)
 8. The abrasive article of claim 2, further comprising asecond latent colorant configured to change color in response toactivation of the cationic photoinitiator. 9-10. (canceled)
 11. Theabrasive article of claim 1, wherein the layer comprises about 10 wt %to about 90 wt % of the epoxy constituent. 12-15. (canceled)
 16. Theabrasive article of claim 1, wherein latent colorant exhibits a specificcolor based on curing of the epoxy constituent.
 17. (canceled)
 18. Anabrasive article comprising: a polymer matrix; a reaction activatedchromophore within the polymer matrix; and particulate abrasive grains.19. The abrasive article of claim 18, wherein the reaction activatedchromophore is formed from a latent colorant and a curing byproduct. 20.The abrasive article of claim 19, wherein the latent colorant isselected from the group consisting of a triaryl methane-based colorformer, a diphenyl methane-based color former, a thiazine-based colorformer, a spiro-based color former, a lactam-based color former, afluoran-based color former, an isobenzofuranone-based color former, andany combination thereof.
 21. The abrasive article of claim 18, whereinthe polymer matrix is free of particulate pigment.
 22. The abrasivearticle of claim 18, wherein the reaction activated chromophorecomprises an organic chromophore.
 23. The abrasive article of claim 18,wherein the polymer matrix comprises a polymerized cationicallypolymerizable constituent. 24-30. (canceled)
 31. The abrasive article ofclaim 18, wherein the polymer matrix comprises a polymerized radicallypolymerizable constituent. 32-37. (canceled)
 38. The abrasive article ofclaim 18, wherein the particulate abrasive grains are selected from thegroup consisting of silica, alumina, zirconia, silicon carbide, siliconnitride, boron nitride, garnet, diamond, cofused alumina zirconia,ceria, titanium diboride, boron carbide, flint, emery, alumina nitride,and any combination thereof.
 39. The abrasive article of claim 38,wherein the particulate abrasive grains have a median grain size between0.1 microns to 1500 microns. 40-41. (canceled)
 42. The abrasive articleof claim 18, wherein the abrasive article is a coated abrasive article.43-44. (canceled)
 45. The abrasive article of claim 42, wherein thecoated abrasive article is an engineered abrasive article.
 46. Theabrasive article of claim 18, wherein the abrasive article is a bondedabrasive article.
 47. The abrasive article of claim 18, furthercomprising a second reaction activated chromophore.
 48. The abrasivearticle of claim 47, wherein the reaction activated chromophore has afirst electromagnetic energy absorption profile and the second reactionactivated chromophore has a second electromagnetic energy absorptionprofile. 49-50. (canceled)
 51. The abrasive article of claim 47, whereinthe reaction activated chromophore is activated based on a differentreaction condition than the second reaction activated chromophore. 52.An abrasive article comprising a reaction activated chromophore.
 53. Theabrasive article of claim 52, wherein the reaction activated chromophoreis formed from a latent colorant and a curing byproduct.
 54. (canceled)55. The abrasive article of claim 52, further comprising a polymermatrix comprising a polymerized cationically polymerizable constituent.56-59. (canceled)
 60. The abrasive article of claim 52, furthercomprising particulate abrasive grains. 61-94. (canceled)